[PATCH 5.17 0732/1126] phy: dphy: Correct lpx parameter and its derivatives(ta_{get,go,sure})

Greg Kroah-Hartman
2022-04-05T08:32:06Z

From: Liu Ying <victor.liu@nxp.com>

[ Upstream commit 3153fa38e38af566cf6454a03b1dbadaf6f323c0 ]

According to the comment of the function phy_mipi_dphy_get_default_config(),
it uses minimum D-PHY timings based on MIPI D-PHY specification. They are
derived from the valid ranges specified in Section 6.9, Table 14, Page 41
of the D-PHY specification (v1.2). The table 14 explicitly mentions that
the minimum T-LPX parameter is 50 nanoseconds and the minimum TA-SURE
parameter is T-LPX nanoseconds. Likewise, the kernel doc of the 'lpx' and
'ta_sure' members of struct phy_configure_opts_mipi_dphy mentions that
the minimum values are 50000 picoseconds and @lpx picoseconds respectively.
Also, the function phy_mipi_dphy_config_validate() checks if cfg->lpx is
less than 50000 picoseconds and if cfg->ta_sure is less than cfg->lpx,
which hints the same minimum values.

Without this patch, the function phy_mipi_dphy_get_default_config()
wrongly sets cfg->lpx to 60000 picoseconds and cfg->ta_sure to 2 * cfg->lpx.
So, let's correct them to 50000 picoseconds and cfg->lpx respectively.

Note that I've only tested the patch with RM67191 DSI panel on i.MX8mq EVK.
Help is needed to test with other i.MX8mq, Meson and Rockchip platforms,
as I don't have the hardwares.

Fixes: dddc97e82303 ("phy: dphy: Add configuration helpers")
Cc: Andrzej Hajda <andrzej.hajda@intel.com>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
Cc: Kishon Vijay Abraham I <kishon@ti.com>
Cc: Vinod Koul <vkoul@kernel.org>
Cc: Heiko Stuebner <heiko@sntech.de>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Guido Günther <agx@sigxcpu.org>
Signed-off-by: Liu Ying <victor.liu@nxp.com>
Link: https://lore.kernel.org/r/20220216071257.1647703-1-victor.liu@nxp.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/phy/phy-core-mipi-dphy.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/phy/phy-core-mipi-dphy.c b/drivers/phy/phy-core-mipi-dphy.c
index ccb4045685cd..929e86d6558e 100644
--- a/drivers/phy/phy-core-mipi-dphy.c
+++ b/drivers/phy/phy-core-mipi-dphy.c
@@ -64,10 +64,10 @@ int phy_mipi_dphy_get_default_config(unsigned long pixel_clock,
cfg->hs_trail = max(4 * 8 * ui, 60000 + 4 * 4 * ui);

cfg->init = 100;
- cfg->lpx = 60000;
+ cfg->lpx = 50000;
cfg->ta_get = 5 * cfg->lpx;
cfg->ta_go = 4 * cfg->lpx;
- cfg->ta_sure = 2 * cfg->lpx;
+ cfg->ta_sure = cfg->lpx;
cfg->wakeup = 1000;

cfg->hs_clk_rate = hs_clk_rate;
--
2.34.1